Stretching machine for dryer felts and the like



T. HINDLE 2, STRETCHING MACHINE FOR DRYER FELTS AND THE LIKE July 5,1960 Filed May 23, 1956 I a. w?

STRETCHING MACHINE FOR DRYER FELTS AND THE LIKE Thomas Hindle,Blackburn, England, assignor to Scapa Dryers Inc., a corporation ofGeorgia Filed'May'23, 1956, Ser. No. 586,697 8 Claims c1. zs- -ss Thisinvention relates to stretching machines for dryerfelts and the like andis particularly, though not exclusively, applicable to machines forstretching, shrinking and'normalizing papermakers dryer-felts.

In papermaking, dryer-felts in the form of endless woven bands are usedto carry the sheet or web of paper in close contact with the dryingcylinders of the paper machine. Although such dryer-felts,- beingcomposed of cotton, of asbestos, of the newer synthetic fibres or of anycombination of these materials, are not subjected to any form of millingand are therefore not felts in the technical sense of the term, theyhave, by common usage, become known as dryer-felts.

Dryer-felts are made in a great variety of widths and lengths, and theapplicants have found, from the accumulated experience of many years,that great advantages are gained when the final stage of theirmanufacture consists of a comb ined stretching, shrinking andnormalizing treatment. The stretching and shrinkingtreatment serves tomake the felt more dimensionally stable for subsequent use on the papermachine, and at the same time the entire substance of the felt isnormalized, that is to say, the local tresses set up in the componentyarns during the weaving process are gently relaxed. Hereinaftertherefore, reference to the stretching process will be understood, whereapplicable, to include the concurrent shrinking and normalizingprocesses.

The dryer-felts used in the paper-makingindustry sometimes attain widthsof twenty-seven feet and lengths approaching five hundred feet, and theoperation of stretching them presents a substantial problem because oftheir great weight. The only known method of stretching such adryer-felt is to wet it thoroughly with water after arranging it to runin the form of an endless band over a plurality of rollers, one or moreof which is heated and one or more of which is capable of being moved toapply longitudinaltension to the dryer-felt.

The existing machine for stretching papermakers dryer-felts consists ofa horizontal frame of sixty feet or more in length, at each end of whichis anupstanding frame carrying a bank of rollers. Mounted in bearingsadjustably movable along the horizontal frame is one or more stretchrollers over which a bight of the felt is reeved so that tension may beapplied to the felt. In order to effect drying of the wetted felt, thelower roller of one bank only is of considerably larger diameter, and issteam-heated. The dryer-felt extends in long horizontal runs between thebanks of rollers and over the stretch rollers.

The length of the felt, as received from the weaver, is drawn intothestretching machine and about the various rollers, and then its ends arestitched or otherwise joined together across the entire width of thefelt to form an endless band preparatory to the actual stretching.

Stretching machines as aforesaid present several operational problems.In the first place there is the time factor as the drying time on suchmachines is commonly in excess of eight hours per dryer-felt. A moredifiicult problem, however, is the control of the sag in the aforesaidlong horizontal runs of the dryer-felt extending between the two banksof rollers and over the stretch rollers, which sag tends to theformation of longitudinal creases as the dryer-felt runs continuouslyover the rollers. When it is realised that some of the largestdryer-felts exceed 1,000 in value, and bearing in mind that there is noknown method by which such creases can be successfully removed, theserious nature of this problem can be better appreciated.

The present invention is based on the appreciation that the principalcause of the aforesaid longitudinal creasing is the transverse sag inthe long unsupported horizontal runs aforesaid of the dryer-felt. In anysuch unsupported horizontal run, the weight of the dryer-felt,especially when thoroughly wetted, causes notonly a longitudinal (i.e.warpways) sag, but also a transverse (i.e. weftways) sag, both sagsapproximating to catenary form. Thus, under these conditions,thestraight-line distance between the selvedges of the transverselysagging dryerfelt is markedly less than the width of thedryer-felt asmeasured without transverse sag. As the dryer-felt runs onto a roller,it attempts to straighten out the transverse sag, but if this is toopronounced, as occurs with long unsupported horizontal, or substantiallyhorizontal, runs, the selvedges do'not move apart to the full width ofthe dryer-felt, in which case. longitudinal creasing occurs at theon-going rollers, causing irreparable damage to the dryer-felt which isthereby rendered useless for its intended purpose. Intermediate supportsto shorten the said unsupported length have been introduced with somemeasure of success, but damage from longitudinal creasing still occursthough the-risk of such damage has been reduced.

The object of the present invention is an improved machine forstretching papermakers dryer-felts and the like, primarily toeliminate-the damage to the dryer-felts by longitudinal creasing,secondarily to speedup the operation, and thirdly a machine of generallyimproved construction having its own inherent advantages.

The invention comprises the method of stretching a papermakersdryer-felt wherein the same is run as an endless band over a pluralityof rollers whilst being subjected to tension, heat or other necessarycondition for its treatment characterized in that the dryer felt isdraped or festooned over spaced elevated supports, before its ends arejoined to form an endless band, so that sub stantially the entire lengthof the band is expended in the formation of downwardly dependingfestoons whose legs are substantially vertical, and which are closed attheir lower ends, and restraining the closed lower end of each festoonfrom upward movement while stretchingforce of such intensity as toincrease the length of the felt is being applied to the felt, wherebytransverse sagging of the felt and the formation of creasesissubstantially prevented.

The invention also comprises a machine for carryingv out the processaforesaid.

According to a preferred embodiment of the invention, a machine forstretching (which, as aforesaid, is to be understood as including theconcurrent shrinking and normalizing processes) paper-makers dryer-feltsand the like, consists of a plurality of pairs ofrollers in upper andlower staggered arrangement, the felt draping over the upper rolls andforming depending festoons closed at their lower ends, and each lowerroller being disposed within the lower .closed end of the correspondingfestoon, thus forming two interleaved pleated formations, at least oneof the rollers being adjustable for tensioning the felt,

tially vertical, and are also relatively short, whereby all possibilityof pronounced sagging of the felt either longitudinally or transverselyis obviated, together with the aforesaid objectionable longitudinalcreasing of the felt.

In theaccompanying drawing:

Fig. l is a diagrammatic illustration of one example of the machine madein accordance with the invention and for use in the stretching,shrinking, and normalizing of papermakers dryer-felts, the end rollersonly of the machine being shown;

Fig. 2 is a front elevation showing mechanism for raising one pair ofrollers for the purpose of tensioning the felt.

The drawings are primarily diagrammatic, all framework being omittedwith the object of clarity. At the lower part of the machine there arepairs of rollers a with the rollersone above the other, and singleendrollers b, whilst at the upper part of the machine there arecomplementary pairs of rollers c. At one end of the machine is alsoshown a pair of upper rollers d similar to the rollers but mounted ateach end in guide blocks e slidably located in guides f at each side ofthe machine. An endless dryer-felt g is shown reeved over and under therollers in two interleaved pleated formations, and motors h are showncoupled to rollers 11 for driving the felt. The rollers d are verticallyadjustable by means of a pair of steel wire ropes i (Fig. 2) eachattached by one of their ends to a winch i and associated at their otherend with a pulley block system k arranged to give mechanical advantageand relatively slow movement, such pulley blocks being connected bylinks m to the sliding blocks 2. The winch j is adapted to be driven bya reversible electric motor 12 through a suitable reduction gearing 0.

At one end of the machine is also shown a guide roller p supported byits ends through steel wire ropes q and winches r, one set only of whichis shown in Fig. 1, for one end of the roller 17. By this means, theroller p may be lowered to have any desired pressure on one end run ofthe felt and by lowering one end more than the other a guiding effecttothe felt may be obtained in known manner. The upper rollers d are shownin their uppermost position whilst their lowermost position is shown indotted lines at d, together with the complementary run of the felt, whenthe rollers are in such lower position. Asshown, the horizontalcomponent of inclination of the run of the dryer-felt between therollers a and c is about /6 of the full length of the run, so that thelegs of each festoon make an angle of not more than 10 with thevertical.

The machine above described may be constructed so that the length of aleg of a festoon, that is to say, the substantially vertical run of thedryer felt between consecutive rollers, will not exceed about fifteenfeet, and will be so steeply inclined as to be substantially vertical. Amachine having eight pairs of upper rollers and seven pairs of lowerrollers will accommodate a dryer-felt in excess of five hundred feet inlength whilst the stretch adjustment provided by one pair of rollers isof the order of thirty feet. By providing stretch adjustment for twopairs of rollers at each end of the machine, there is ample provisionfor all the stretch requirements for the largest dryer-felts at presentmanufactured or contemplated.

It will be evident from inspection of the drawings, that the rollers a,b, c, d, etc. about which the felt passes are cylindrical and devoid ofperipheral ribs or grooves, and although the surfaces of these rollersneed not be polished, and in fact may, if desired, be such as to exert africtional effect upon the felt, the rollers are herein referred to assmooth-surfaced to distinguish from rollers having distinct peripheralribs or grooves.

. The machines also require provision for heating one or more of therollers during the operation of stretching chines, in which thedryer-felt has long horizontal runs,

the heat applied to the dryer-felt is lost too quickly. With the newarrangement of the rollers, however, ac-

cording to the present invention, heat which may be applied through anynumber of rollers, for example through some or all of the lower rollersa, is relatively far as such details may be modified without departingand drying the dryer-felts. In the case of existing mafrom the scope ofthe invention. For instance, a second adjustable guide roller may beprovided at the other end of the machine from that shown whilst furtherintermediate guide rollers may be provided, if found necessary, toensure correct running of the dryer-felt on the rollers during thestretching operation. It is believed, however, that one such roller ateach end will suffice for the purpose. Also, the raising of thestretching rollers could be effected by means other than the steel wirerope and pulley mechanism shown though such mechanism has the advantageof simplicity and there is every reason to believe that it will givecomplete satisfaction.

A further advantage of the machine constructed in accordance with theinvention is that the provision of driving rollers and stretching andguiding equipment at each end of the machine allows for the processingof two dryer-felts at the same time, one at each end of the machine,providing that the sum of the lengths of the two felts does not exceedthe total length capacity of the machine. The motors h may be arrangedto drive additional rollers a in the lower bank as shown dotted in Fig.1.

The basic principle of the invention lies in the appreciation that theelimination of the long horizontal runs found in previously knownmachines, will result in the elimination of damage by longitudinalcreasing of the dryer-felts during the stretching and normalizingtreatment. The steeply inclined and relatively shorter runs of thedryer-felt between the upper and lower rollers are substantiallyvertical and consequently transverse sagging of the dryer felt under theaction of gravity, which has been the principal cause of thelongitudinal creasing of the dryer-felt, is therefore reduced to anegligible quantity. It is also to be appreciated that the improvedstretching machine herein described may be operated, with equal safetyto the dryer-felt, in either direction, consequently, the motors h maybe reversed several times during the stretching and drying operation inorder to ensure that the weft in the finished dryer-felt shall bestraight and not bowed.

I claim:

1. Method of treating a paper-makers dryer-felt, including theapplication of longitudinal tension, after the felt has been woven,thereby to make the felt dimensionally stable while avoiding transversesagging and the consequent formation of longitudinal creases, saidmethod comprising as steps, draping the felt over a series ofhorizontally spaced elevated supports to form festoons whose legs aresubstantially vertical, joining the ends of the felt to form an endlessband, restraining the closed lower end of each festoon from upwardmovement, applying stretching force to the felt of such intensity as toincrease the length of the felt, and moving the felt in the direction ofits length while the stretching force is being applied.

2. Method, according to claim 1, wherein two rows of elevated supportsare provided, and the felt is draped over both rows of supports so as toprovide pairs of downwardly depending festoons, with one festoon of apair disposed within the other festoon of the same pair.

3. Apparatus for use in the manufacture of a papermakers dryer-felt,including the application of longitudinal tension thereto, after thefelt has been woven and after its ends have been joined to form anendless band, thereby to make the felt dimensionally stable whileavoiding transverse sagging and the consequent formation of longitudinalcreases, said apparatus comprising supporting means over which the feltmay be draped, before its ends have been joined, to form downwardlydepending festoons, each festoon being closed at its lower end, and withthe legs of each festoon diverging upwardly at an angle notsubstantially exceeding to the vertical, said apparatus comprising anupper series of horizontally spaced, parallel, horizontal, elongate,smooth-surfaced felt-positioning elements and a lower series ofhorizontally spaced, parallel, horizontal, smooth-surfacedfeltpositioning elements, the elements of the upper series beingstaggered with relation to those of the lower series, the positioningelements of the lower series constituting restrainers each operative toprevent upward motion of the closed lower end of a corresponding festoonof the festooned material, and each element of the upper seriesconstituting a support over which the felt may be draped, one of thefelt-positioning elements of the upper series being bodily movableupwardly, and means for moving said movable element upwardly, relativelyto the other elements of the upper series, with force suflicient toincrease the length of the felt.

4. Apparatus, according to claim 3, wherein the feltpositioning elementsare smooth-surfaced cylindrical rolls whose axes are parallel, andreversible motor means for turning certain, at least, of said rollsthereby to traverse the felt alternately in opposite directions whilethe longitudinal stretching force is being applied.

5. Apparatus, according to claim 3, wherein the number of said elevatedpositioning elements is such that when used for stretching a felt of theorder of five hundred feet in length, the length of the materialconstituting each respective leg of a single bight need not exceedfifteen feet.

6. Apparatus for treating paper-makers dryer-felt according to claim 3characterized in that the means for tensioning the dryer-felt comprisesat least one tension roller, journals for the ends of the roller, cablessuspending said joumals and a common winch for winding said cables.

7. Apparatus for use in the manufacture of a papermakers dryer-felt toimpart dimensional stability thereto, while avoiding the formation oflongitudinal creases therein, said apparatus comprising horizontallyspaced pairs of rollers forming an upper series, and horizontally spacedpairs of rollers forming a lower series, one roller of each pair beingdirectly above the other, and the lower pairs being staggered withreference to the upper pairs, the rollers providing means about which anendless dryerfelt, of a length as great as five hundred feet, may becompactly reeved in two interleaved, pleated formations, at least one ofthe rollers benig bodily movable, and means for applying force for somoving said last-named roller as to increase the length of the felt, thearrangement being such that the runs of material, extending between aroller of an upper pair and a corresponding roller of a lower pair, areso steeply inclined as to be substantially vertical, and the number ofrollers being such that the maximum length of any run of such a felt,extending from a roller of an upper pair to the corresponding roller ofa lower pair, need not exceed fifteen feet, whereby all possibility ofsagging of the felt either longitudinally or transversely withconsequent creasing is obviated.

8. Apparatus for use in the manufacture of a papermakers dryer-felt,including the application of longitudinal tension thereto after the felthas been woven and after its ends have been joined to form an endlessband, thereby to stretch the felt longitudinally and to normalize itsstructure, said apparatus comprising means operative so to position thematerial of the felt as to form pairs of downwardly directed festoons,each closed at its lower end and each having upwardly directed legswhich are within approximately 10 of the vertical, one festoon of eachpair being nested within but spaced from the other festoon of the samepair, the means for so positioning the material of the felt so as toform a series of nested downwardly depending festoons comprising anupper series of horizontally spaced pairs of felt positioning elementsand a lower series of horizontally spaced pairs of felt-restrainingelements, each lower restraining element of each pair being disposedwithin the closed lower end of the outer festoon of a nested pair, andthe upper restraining element of each pair being disposed within theclosed lower end of the inner festoon of a pair of nested festoons.

References Cited in the file of this patent UNITED STATES PATENTS634,307 Neidhardt Oct. 3, 1899 813,288 Hancock Feb. 20, 1906 1,137,719Sibson Apr. 27, 1915 FOREIGN PATENTS 560,061 Germany Sept. 28, 1932

